Conventional in-line filter vessel designs provide in-line nozzles at the same elevation or at different elevations. As shown in FIG. 1A, a conventional filter vessel 10 with in-line inlet and outlet nozzles 12, 14 positioned at the same elevation allow for a straight line arrangement of the filter vessel 10 within a process or system and requires no deviation of the process piping from its original elevation. Typically, this design requires that an inlet pipe 16 protrude through the tube sheet 18 of the filter vessel 10. Thus, the inlet pipe 16 occupies space which could otherwise be occupied by a filter element 20. As a result of the inlet pipe 16 requiring the displacement of at least one filter element 20, larger filter vessel diameters are needed for a given number of filter elements 20. In small diameter vessels, in particular, this significantly diminishes the filter capacity for a given filter vessel diameter or requires a larger diameter filter vessel 10 to achieve a given capacity, requiring both greater vessel space (which is often at a premium in process designs) and greater fabrication cost. In packaged process systems, minimization of space can be an important design element in terms of minimizing material costs as well as overall system costs. These effects are particularly acute in applications where footprint and/or weight are extremely costly, such as offshore oil and gas production platforms. Depending on the design pressure of the filter vessel 10, a larger vessel diameter may also require a greater shell thickness in order to conform to design codes, further increasing material requirements, vessel weight, and fabrication costs.
FIG. 1B shows a conventional filter vessel 10 with in-line nozzles 12, 14 positioned at different elevations. This can allow maximization of filter elements 20 within the filter vessel 10, but does so at the expense of the nozzle elevation. More specifically, to afford an inlet that does not protrude through the tube sheet 18 and occupy filter space, the inlet nozzle 12 is elevated relative to the outlet nozzle 14. This arrangement requires additional piping complexity (such as elbows and risers) and additional piping space around the filter vessel 10, increasing its overall footprint. Additionally, fabrication code requirements may necessitate spacing between welds, closures, etc., which results in further additional height accommodations. The added height typically does not allow personnel to access the filter elements 20 when standing at grade, necessitating access platforms 19, ladders, etc. (as shown in FIG. 2). Additionally, the vessel design of FIGS. 1B and 2 places the filter elements 20 well below the vessel closure 21. By most process plant safety requirements, placing any part of the body below the vessel closure 21 constitutes a confined space vessel entry, requiring additional safety procedures and insertion of blinds into the process piping. This may add considerable operational burden and time required to replace filter elements 20, diminishing plant productivity. The vessel arrangement also results in a large liquid hold-up volume above the tube sheet 18. In the event that the liquid being filtered is a high value product, this may lead to unacceptable product losses. If the liquid being filtered is hazardous or contains volatile, poisonous components (such as hydrogen sulfide gas), this may lead to significant personnel exposure to dangerous materials when opening the filter vessel.